Not really a bug, but I just upgraded to the last version, and I had to make changes to three projects, they all gained roughly 15% in file sizeI haven't worked in C2 for a while (nor have the time for further tests these days), so this may not have been introduced in the very last version...I noticed r123 had an updated Google Closure Compiler, which may be worse than the previous version?

Closing as not a bug, this is all the save/load machinery. I tried to design it so Closure Compiler would omit it if it wasn't used, but it proved rather difficult to do that. I don't think it's too important anyway, since most servers transmit HTML, JS and CSS in compressed format, so the actual transmitted size will be roughly equivalent to the size of zipping the file. An empty project exports to ~93kb minified, and compresses down to just 30kb, so I think in practice the runtime script will be about as big as one or two images from your project.